Refactoring: Save connection as object with color as property.
Show notifications for adding and deleting items.
Show notifications for successful uploading.
Allow overriding the server JSON data via "Upload".
Allow overriding the client data via "Download", to re-establish a
connection after having been offline.
Upload/Download button fixed on bottom of the page, not under the input
field.
Only show "Download" and "Upload" buttons if OFFLINE!